In general, a motor includes a stator and a rotor. A small motor is constructed in such a manner that a permanent magnet is used as a stator, a coil is wound around a rotor and current is applied to the coil to make the rotor function as a permanent magnet such that the rotor rotates according to interaction between the stator and the rotor. In this structure, current is continuously supplied to the rotor even while the rotor rotates by means of a brush.
With the recent development of semiconductors, a permanent magnet is used as a rotor, a coil is wound around a stator and power is supplied to the stator. According to this structure, stators are sequentially magnetized to rotate the rotor magnetically corresponding to the stators. A motor of this type is called a permanent magnet synchronous motor (PMSM). The PMSM can minimize power consumption and improve system efficiency because a permanent magnet is used as a rotor to generate magnetic flux without using an external power supply.
The structure of the PMSM can be classified according to arrangement of a rotor and a stator. Particularly, a surface-mounted permanent magnet motor (SPM) having a permanent magnet attached to the surface of a rotor generates sinusoidal back electromotive force through the permanent magnet attached to a cylindrical shaft. The SPM generates a constant torque all the time when sinusoidal current is applied to an armature coil.
In a conventional motor structure, a stator coil is covered by an insulator such that inter-turn short circuit fault is not generated between the stator coil and a neighboring coil. However, the insulator covering the coil may age over time or be damaged due to power or spark induced into the motor. Accordingly, the insulator may be stripped off to expose the coil and the exposed coil and a neighboring exposed coil are short-circuited. To solve this coil turn circuit, a conventional fault detection method detects a motor fault only on the basis of a case in which power of a predetermined level is not output in initial operation of a motor, and thus the cause of the motor fault cannot be correctly detected and it is difficult to appropriately control the motor. Furthermore, since the conventional fault detection method experimentally applies a predetermined reference level, a considerable deviation and error are generated. To reduce the deviation and error, a large amount of experimental data needs to be acquired and thus efforts and expenses for the same are required.